The present invention relates to a controlling agent and a controlling method for plant disease and, more particularly, it relates to a controlling agent and a controlling method for plant disease where a lactic acid bacterium seemingly advantageous to human health is used whereby disease of agricultural crop is able to be suppressed. The invention also relates to a treating method for plant and/or soil using the specific lactic acid bacteria.
In recent years, application of biological control which is a control using a useful microorganism has been investigated to plant diseases which are difficult to control by synthetic agricultural chemicals. There has been also a strong demand for agricultural methods considering in environments or, in other words, agriculture of an environment conservation type (sustainable agriculture) and a biological control using a useful microorganism has been positively investigated with an object of suppression of use of chemically synthesized agricultural chemicals.
For example, in the following Patent Documents 1 to 3, control techniques for plant diseases using microorganisms belonging to the genus Pseudomonas are proposed. In the following Patent Document 4, there is a proposal for a technique of controlling the plant diseases by the joint use of an actinomycete having an antagonistic property to causing microorganism for soil disease and a microorganism producing viscous substances. In the following Patent Document 5, there is a proposal for controlling the plant diseases by the joint use of a microorganism belong to the genus Cladsporium and a microorganism belong to the genus Bacillus. 
Patent Document 1: Japanese Patent No. 3,431,926 (JP-A-5-916)
Patent Document 2: Japanese Patent No. 2,533,828 (JP-A-6-9325)
Patent Document 3: Japanese Patent No. 3,135,708 (JP-A-6-107511)
Patent Document 4: JP-A-2003-277212
Patent Document 5: JP-A-2003-300803
Patent Document 6: JP-A-10-164987
When a microorganism used for a purpose of control of plant diseases is sold by indicating its control effects, it is necessary to register it as agricultural chemicals in accordance with the Agricultural Chemicals Regulations Law of Japan. In the registration of agricultural chemicals, examinations for safety such as evaluation of influence to human, animals/plants and natural environment are essential in addition to a control effect on plant diseases, and only the microorganism which passes the examinations is able to be registered and sold as agricultural chemicals.
Further, under the circumstance where interest of consumers in safety of “food” is increasing, interest is also paid to a microorganism in food, and consideration in such a point is also an important problem in agricultural crop which is subjected to a disease control utilizing the useful microorganism.
On the other hand, in view of an increase in consciousness of “health” by consumers, functional components useful to human body and food containing such components are becoming popular. Among them, public interest is also increasing in lactic acid bacteria which are said to have effects such as a calming action to intestinal disorder and a suppressive action to cancer.
Under such circumstances, if diseases of agricultural crop are able to be controlled using a lactic acid bacterium which is said to be useful for human health, no problem in a safety examination for the registration of agricultural chemicals is resulted, anxiety of consumers to safety is cleared away and, further, properties in function and as commercial product of the agricultural crop are enhanced whereby that will become an ideal control of diseases.
The present invention has been achieved in view of the above and its object is to provide a controlling agent and a controlling method for plant disease using a lactic acid bacterium which is seemingly advantageous to human health as well whereby production of agricultural crop in safe, assured and stable manner is now possible.
In the aforementioned Patent Document 6, there is a proposal of a cultivating technique for plant. This technique relates to a cultivating method where cultivating environment is able to be artificially controlled in a cultivating process from the stage of seeds to the stage where shipping is possible (such as hydroponics). In the method, after plant is washed, a lactic acid bacterium as a microorganism which is non-toxic to human body is fixed on the surface of the plant and the plant surface is covered by the lactic acid bacterium whereby invasion and proliferation of miscellaneous microorganisms and pathogenic microorganisms are suppressed. However, this technique relates to a food preservation technique called bio-preservation and the lactic acid bacterium used is for such a purpose that plant such as white radish sprout is not polluted by microorganism which is harmful to human (such as Escherichia coli). Therefore, that is a technique which is clearly different from the present invention where cultivation in a farm under the environment in which numerous microorganisms are present is main and a lactic acid bacterium is used for controlling the plant disease which is a disease of plant itself.
In the Patent Document 4, use of a microorganism belonging to the genus Lactobacillus is disclosed but this microorganisms is mentioned in such a manner that the microbe itself has no control effect on plant diseases but it is a microorganism producing a viscous substance jointly used with actinomycete which is an antagonistic microorganism. Accordingly, this document does not suggest that a lactic acid bacterium has a control effect on plant diseases such as soil disease.